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In this work, a comparative degradation analysis of high-efficiency inverted organic solar cells (iOSCs) is presented, with the PTB7-Th:PC70BM blend as the active layer and hole transport layers (HTLs), of V2O5, MoO3 and their stacks. Five groups of iOSCs, were fabricated with V2O5 (3 nm), V2O5/MoO3 (3/1 nm), V2O5/MoO3 (3/2 nm), V2O5/MoO3 (3/5 nm) and MoO3 (10 nm), respectively. The performance parameters obtained from illuminated J–V curves of the devices were analyzed. The long-term operational stability of encapsulated iOSCs is studied following the ISOS-D1 protocols for 19 600 h. The maximum PCE obtained using stacks of V2O5/MoO3 (3/1 nm) is 10.58%. The best stability was obtained for devices using 10 nm MoO3 as the HTL, for which after 19 600 h, the PCE reduced to 51%. The cell using 3 nm V2O5 degraded to 50% of its initial PCE (T50) after only 775 hours. The use of stacks of V2O5/MoO3 (3/1 nm), V2O5/MoO3(3/2 nm), V2O5/MoO3 (3/5 nm), increased the long-term stability of iOSCs, with T50 values equal to 3140 h, 4865 h, and 6808 h, respectively. Our study provides the details of the causes of the differences in behavior observed for the different materials used as HTLs. Although the physical degradation mechanism seems to be the same, the intensity is lower as the MoO3 thickness increases, which acts as a diffusion barrier reducing the diffusion rate of O2 and H2O toward the active layer. The impedance spectroscopy measurements confirm that, in this study, the degradation of the active layer is the main cause of decrease in performance of the device.

Analysis of stability and degradation of inverted organic solar cells (iOSCs) formed by the blend PTB7-Th:PC70BM, with different stacks of electron transport layers (ETLs) PFN, PFN/LiF, LiF/PFN, LiF and without one are manufactured under N2 environment. The degradation study of the iOSCs is done following ISOS-D1 protocols under air environment, up to 7110 h. Performance parameter obtained from J-V curves such as open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF) and power conversion efficiency (PCE) are analyzed for each group of iOSCs with the above mentioned different stacks of ETLs and compared between of them. The cell manufactured with the stack PFN/LiF shows the highest stability over time and its TS80 is reached to 201 h. Cells with the stack LiF/PFN and PFN show their TS80 to 153 h and 144 h, respectively. The S-shape is presented on all J-V curves under study and are modeled using an equivalent circuit of three-diodes, in order to understand the physical mechanism related to it.

In this work, stability and degradation of inverted organic solar cells (iOSCs) partially manufactured under air environment are analyzed. The degradation of iOSCs fabricated with inkjet printed ZnO and with spin coated PFN as electron transport layer (ETL) is compared. The PTB7 and PC70BM materials are used as donor and acceptor in the active layer, respectively, for all photovoltaic devices. During all the degradation study of the iOSCs, performance parameters such as open circuit voltage (VOC), short circuit current density (JSC), fill factor (FF) and Power conversion efficiency (PCE), are extracted from the current density - voltage measurements (J-V) under dark and light conditions. The PCE of the unencapsulated iOSCs with PFN as ETL, left under N2, decreased to 80% after 58 h, while the same PCE reduction for iOSCs with inkjet printed ZnO as ETL, occurred after 189 h. Under air environment, the PCE of unencapsulated iOSCs fabricated with ZnO as ETL devices decreases to 80% after 160 h.

In this study, we report the use of Hafnium-Indium-Zinc-Oxide (HIZO) as electron transport layer (ETL) in inverted organic solar cells (iOSCs) using a bulk heterojunction of Poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7) and [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) as active layer. The absorption spectrum and performance parameters obtained are compared to those obtained for similar iOSCs where the ETL was poly [(9,9-bis (30- (N,N-dimethylamino) propyl) -2,7-fluorene) -alt-2,7- (9,9-dioctylfluorene)] (PFN). Initially, devices showed the S-shaped current–voltage curve that has been modeled using a three-diode equivalent circuit model. This phenomenon can be removed by repeating electrical sweep-cycles under illumination. The degradation under nitrogen atmosphere and under encapsulation was also analyzed and compared with the degradation of the iOSCs using PFN. It was observed that the degradation of encapsulated HIZO-iOSC was twice slower than that of PFN-iOSCs. This increase in stability can be attributed to the Hf atoms, which have a stronger thermodynamic tendency to form metal oxides, suppressing the dissociation of HIZO.

In this study, we report the use of poly [(9,9-bis (30- (N,N-dimethylamino) propyl) -2,7-fluorene) -alt-2,7- (9,9-dioctylfluorene) (PFN) as hole blocking layer (HBL) in inverted small-molecule solar cells (SM-iOSCs) using a bulk heterojunction of p-DTS(FBTTh 2 ) 2 as donor material and PC 70 BM as acceptor material. The behavior of these devices is compared to those SM-iOSCs where the HBL was zinc oxide (ZnO). Under 1 sun illumination, devices exhibited a power conversion efficiency (PCE) of 6.75%. It is demonstrated, through analysis of the external quantum efficiency (EQE), abortion UV-vis and atomic force microscopy of the active layer, that charge transport is the limiting factor in the performance of the cells, directly affecting the short circuit current (J SC ).

The effects of hafnium oxide (HfO2) as hole blocking layer (HBL) on the stability and degradation under air environment of inverted bulk heterojunction organic solar cells (iOSC), using as donor material thieno[3,4b]thiophene-alt-benzodithiophene (PTB7) and as acceptor material [6], [6]-phenyl C71 butyric acid methyl ester (PC 70 BM) are presented. The ultrathin films of HfO 2 layers 0.9 nm of thick were deposited by thermal evaporation. The highest power conversion efficiency obtained (PCE) was of 8.33%. The current density-voltage characteristic (J-V) was modeled through the ideal-diode equivalent circuit model. For comparison, cells with poly [(9,9-bis (30- (N,N-dimethylamino) propyl) −2,7-fluorene) -alt-2,7- (9,9-dioctylfluorene)] (PFN) and Zinc Oxide (ZnO) as hole blocking layer were fabricated. The three groups of cells were exposed to air for 1000 h. The electrical parameters extracted from the current density-voltage characteristic (J-V) were analyzed. The PCE for cells manufactured with HfO 2 as HBL remains around 30% after 1000 h under air environment, showing less degradation than iOSCs with ZnO.

In this work, we analyze the stability and degradation over time of inverted organic solar cells (iOSCs) using a stack layer of vanadium oxide and nickel oxide as hole transport layers (HTL). The parameter used to compare with other cells is the power conversion efficiency (PCE). Vanadium oxide layer (V 2 O 5 ) used as HTL is the reference in this work which is monitored the stability and degradation. All devices are fabricated under nitrogen environment. The stack layer thickness used as HTL is fabricated with NiO on V 2 O 5 layer, which has been varied. The photovoltaic devices are encapsulated to be studied their degradation over time following the ISOS-D1 protocols during 10200 h. The active layer for devices is a mix of PTB7-Th and PC70BM being the donor and acceptor material, respectively. The performance parameters under light during the degradation process are extracted from the current density - voltage (J-V) characteristics. The PCE of iOSCs manufactured with the stack V 2 O 5 / NiO (0.5 nm), V 2 O 5 /NiO(1 nm) and V 2 O 5 /NiO(0 nm) reached the 80% (T S80 ) after 1600 h, 190 h and 84 h, respectively.

In this work, we fabricate, characterize and present a stability study of p-DTS(FBTTh2)2:PC70BM inverted organic solar cells (iOSCs) with two different solution-processed electron transport layers (ETLs), PFN and ZnO, under indoor light and AM 1.5 G illumination spectrum. A warm white color light-emitting diode was used as the indoor light source. Under the luminance of 1000 lux, a maximum power conversion efficiency (PCE) of 10.85% and maximum power density (MPP) of 45.1 μW/cm2 were obtained for cells with PFN as ETL. After 1536 h of constant indoor light illumination, the PCE remained above 70% of the original value. The best stability of encapsulated devices, under AM 1.5 illumination spectrum was also observed for these cells, which still maintained a PCE above 60% after 6000 h.

In this study, we analyze the stability and degradation of inverted organic solar cells (iOSCs) partially fabricated under air environment. It is compared the degradation of iOSCs manufactured with PFN against inkjet printed ZnO as electron transport layer (ETL). The active layer use PTB7 and PC70BM as donor and acceptor material, respectively for all devices. The electrical parameters during the degradation process were extracted from the current density - voltage characteristics (J-V) under light and dark conditions. The power conversion efficiency (PCE) of the devices under nitrogen without encapsulation decreased down to 80% after 58 h for iOSCs with PFN and after 189 h for inkjet printer ZnO. Photovoltaic devices under air and without encapsulation manufactured with ZnO, the PCE decrease to 80 % after 160 h.

In this work, the degradation of inverted bulk heterojunction organic solar cells (BHJ-OSC) exposed under solar and under artificial irradiance conditions is studied. The photovoltaic devices were based on the polymer PTB7 and the fullerene PC 70 BM and partially fabricated under air environment. The current density-voltage (J-V) characteristics of the devices were obtained at room temperature, under both dark and illumination conditions for a period of up to 1344 h. The samples were stored, between measurements, in a glove box under nitrogen environment.