The record efficiencies of perovskite solar cells (PSCs) have been led by increasing open-circuit voltage (VOC) in their current-voltage performance as the result of minimized loss in defect-assisted charge recombination that is mostly associated with heterojunction interfaces and grain boundaries.1 Therefore, interfacial management to ensure high VOC is essential to enhancing power conversion efficiency (PCE) of the perovskite devices that undergo large recombination losses. In organic-inorganic hybrid perovskite devices, we showed a method to enhance PCE by modifying the perovskite-hole transport layer (HTL) interface with an array of dipole-inducing organic molecules, which enables high VOC (close to SQ theoretical limit) with PCE&gt;22%.2 While high PCE is obtainable with hybrid perovskites, organic cations of perovskites and use of diffusible dopants in HTL materials are often responsible for low stability of perovskites at high temperatures (&gt;120oC). In this respect, use of all-inorganic perovskite materials and dopant-free HTMs is strongly desired for future industrialization. We have focused our device fabrication on use of all-inorganic CsPbX3 (X=I, Br) perovskites in combination of dopant-free HTMs. These halide perovskites are thermally stable up to &gt;400oC while relatively large VOC loss of the CsPbX3-based devices has been a challenge for improvement. We conducted compositional modification of the junction interfaces of CsPbX3. By introducing an amorphous SnOx nanosheet to the perovskite-electron transport layer (ETL) interface to intensify the hole-blocking effect, CsPbI3Br (bandgap, 1.9 eV) PSCs achieved PCEs of &gt;17% with VOC in excess of 1.4V under 1 sun and &gt;34% under indoor LED illumination with VOC &gt;1.1V.3 In the method to passivate the perovskite-HTL interface with thiophene derivatives that react with iodine vacancy defects, CsPbI1.5Br1.5 cell and CsPbIBr2 cell yield VOCs of 1.51 V (90% of SQ limit) and 1.54 V (87% of SQ limit), respectively. Our trials in interfacial passivation using functional organic molecules for high Voc photovoltaics will be summarized.

Interfacial molecular passivation for high Voc perovskite photovoltaics

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ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.