Search

All‐inorganic CsPbI3 quantum dots (QDs) have shown great potential in photovoltaic applications. However, their performance has been limited by defects and phase stability. Herein, an anion/cation synergy strategy to improve the structural stability of CsPbI3 QDs and reduce the pivotal iodine vacancy (VI) defect states is proposed. The Zn‐doped CsPbI3 (Zn:CsPbI3) QDs have been successfully synthesized employing ZnI2 as the dopant to provide Zn2+ and extra I−. Theoretical calculations and experimental results demonstrate that the Zn:CsPbI3 QDs show better thermodynamic stability and higher photoluminescence quantum yield (PLQY) compared to the pristine CsPbI3 QDs. The doping of Zn in CsPbI3 QDs increases the formation energy and Goldschmidt tolerance factor, thereby improving the thermodynamic stability. The additional I− helps to reduce the VI defects during the synthesis of CsPbI3 QDs, resulting in the higher PLQY. More importantly, the synergistic effect of Zn2+ and I− in CsPbI3 QDs can prevent the iodine loss during the fabrication of CsPbI3 QD film, inhibiting the formation of new VI defect states in the construction of solar cells. Consequently, the anion/cation synergy strategy affords the CsPbI3 quantum dot solar cells (QDSC) a power conversion efficiency over 16%, which is among the best efficiencies for perovskite QDSCs. [ABSTRACT FROM AUTHOR]

A synergistic approach combining new material design and interfacial engineering of devices is adopted to produce high efficiency inverted solar cells. Two new polymers, based on an indacenodithieno[3,2- b]thiophene-difluorobenzothiadiazole (PIDTT-DFBT) donor-acceptor (D-A) polymer, are produced by incorporating either an alkyl thiophene (PIDTT-DFBT-T) or alkyl thieno[3,2-b]thiophene (PIDTT-DFBT-TT) π-bridge as spacer. Although the PIDTT-DFBT-TT polymer exhibits decreased absorption at longer wavelengths and increased absorption at higher energy wavelengths, it shows higher power conversion efficiencies in devices. In contrast, the thiophene bridged PIDTT-DFBT-T shows a similar change in its absorption spectrum, but its low molecular weight leads to reduced hole mobilities and performance in photovoltaic cells. Inverted solar cells based on PIDTT-DFBT-TT are explored by modifying the electron-transporting ZnO layer with a fullerene self-assembled monolayer and the MoO3 hole-transporting layer with graphene oxide. This leads to power conversion efficiencies as high as 7.3% in inverted cells. PIDTT-DFBT-TT's characteristic strong short wavelength absorption and high efficiency suggests it is a good candidate as a wide band gap material for tandem solar cells. [ABSTRACT FROM AUTHOR]