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In thin‐film photovoltaics, such as organic and perovskite solar cells, charge extraction selectivity is crucial. In order to improve selectivity, charge transporting layers (doped and undoped) are frequently used; however, it is not well understood how a charge transporting layer should be designed in order to ensure efficient extraction of majority carriers while blocking minority carriers. This study clarifies how well charge transporting layers with varying majority carrier conductivities block minority carriers. The charge extraction by a linearly increasing voltage technique is used to determine the surface recombination velocity of minority carriers in model system devices with varying majority carrier conductivity in the transporting layer. The results show that transporting layers with high conductivity for majority carriers do not block minority carriers—at least not at operating voltages close to or above the built‐in voltage, due to direct bimolecular recombination across the transporting layer–absorber layer interface. Design principles are furthermore discussed and proposed to achieve selective charge extraction in thin‐film solar cells using charge transporting layers.

Organic solar cells, despite their high power conversion efficiencies, suffer from open circuit voltage losses making them less appealing in terms of applications. Here, the authors, supported with experimental data on small molecule photovoltaic cells, relate open circuit voltage to photovoltaic gap, charge-transfer state energy, and donor-acceptor interfacial morphology.

There has been a recent surge in interest toward thin film-based solar cells, specifically new absorber materials composed by Earth-abundant and non-toxic elements. Among these materials, antimony selenide (Sb2Se3) is a good candidate due to its peculiar properties, such as an appropriate bandgap that promises a theoretical maximum power conversion efficiency of 33% and an absorption coefficient of around 105 cm−1, enabling its use as a thin film absorber layer. However, charge carrier transport has been revealed to be problematic due to its cumbersome structure and the lack of a doping strategy. In this work, we aim to provide a clear picture of the state-of-the-art regarding research on Sb2Se3-based solar cells and its prospects, from the successful achievements to the challenges that are still to be overcome. We also report on the key parameters of antimony selenide with a close focus on the different characteristics associated with films grown from different techniques.

Photomutiplication-type organic photodetectors (PM-OPDs) are attractive for various next-generation technologies due to their lower cost, higher sensitivity and technological utility. Here, the authors report vacuum-processed narrowband PM-OPDs with enhanced sub-bandgap external quantum efficiency.

The commercialisation of organic photovoltaic technology calls for research on material degradation mechanisms. Ramirez et al. show that triplet excitons produced by back charge transfer can significantly impact the photo-stability of fullerene-based devices even in the absence of water and oxygen.

The suppression of dark current in organic photodetectors (OPDs) is important for maximizing the performance of the devices. Here, the authors report the relationship between the high dark saturation current and the presence of mid-gap trap states in OPDs with a donor–acceptor structure.

Though single-material organic solar cells are attractive for next-generation photovoltaic technologies, designing new materials with ideal properties remains a challenge. Here, the authors report the use of orientation-dependent molecular electrostatics to realise efficient homojunction devices.

Strong light-matter coupling can tune exciton properties but its effect in photovoltaics remains unexplored. Here Nikolis et al. show that the photon energy loss from optical gap to open-circuit voltage can be reduced to unprecedented values by embedding organic solar cells in optical microcavities.

Abstract A method to determine the doping induced charge carrier profiles in lightly and moderately doped organic semiconductor thin films is presented. The theory of the method of Charge Extraction by a Linearly Increasing Voltage technique in the doping-induced capacitive regime (doping-CELIV) is extended to the case with non-uniform doping profiles and the analytical description is verified with drift-diffusion simulations. The method is demonstrated experimentally on evaporated organic small-molecule thin films with a controlled doping profile, and solution-processed thin films where the non-uniform doping profile is unintentional, probably induced during the deposition process, and a priori unknown. Furthermore, the method offers a possibility of directly probing charge-density distributions at interfaces between highly doped and lightly doped or undoped layers.

Interfaces of organic donor-acceptor blends provide intermolecular charge-transfer states with red-shifted but weak absorption. By introducing an optical micro-cavity; Siegmundet al., enhance their photoresponse to achieve narrowband NIR photodetection with broad spectral tunability.

Three furan-fused BODIPYs were synthesized with perfluorinated methyl, ethyl and n-propyl groups on the meso-carbon. They were obtained with high yields by reacting the furan-fused 2-carboxylpyrrole in corresponding perfluorinated acid and anhydride. With the increase in perfluorinated alkyl chain length, the molecular packing in the single crystal is influenced, showing increasing stacking distance and decreasing slope angle. All the BODIPYs were characterized as intense absorbers in near infrared region in solid state, peaking at ~800 nm with absorption coefficient of over 280 000 cm-1. Facilitated by high thermal stability, the furan-fused BODIPYs were employed in vacuum-deposited organic solar cells as electron donors. All devices exhibit PCE over 6.0% with the EQE maximum reaching 70% at ~790 nm. The chemical modification of the BODIPY donors have certain influence on the active layer morphology, and the highest PCE of 6.4% was obtained with a notably high jsc of 13.6 mA cm-2. Sensitive EQE and electroluminance studies indicated that the energy losses generated by the formation of a charge transfer state and the radiative recombination at the donor-acceptor interface were comparable in the range of 0.14-0.19 V, while non-radiative recombination energy loss of 0.38 V was the main energy loss route resulting in the moderate V∞ of 0.76 V. [ABSTRACT FROM AUTHOR]