n-type polyaniline hole-blocking layer for high-efficiency QDSC by one-pot electropolymerization and selective aprotic cation ([EMIM]⁺) doping

In the field of clean solar-to-current devices, the photoelectron transfer process is essential for photovoltaic conversion in the typical n-i-p solar-cell structure. With regard to the oriented injection and ejection of photoelectrons, the development of hole-blocking layer (HBL) materials with a high electron transfer capability are exceedingly desirable. Profiting from the distortion of the p-π electron cloud attracted by a doped aprotic cation, a modified n-type polyaniline (PANI) as the HBL of a photoanode has been successfully fabricated through a facial one-pot square-wave potentiostatic electropolymerization method. In terms of flat-band potential, charge-carrier concentration and device impedance, the synthesized n-type polyaniline layer doped by aprotic ionic liquid (AIL; [EMIM] [EtSO₄]) (AIL–PA layer) for quantum dot solar cells (QDSCs) directly facilitates the high electron carrying capacity as well as the electron transfer driving force. Furthermore, the n-type polyaniline layer doped by AIL ([EMIM] [EtSO₄]) (AIL–PA layer) has a widely matching band gap for electron exportation and improved photovoltaic performance of CdS_xSe_1-x QDSCs: the power conversion efficiency is 10.5% and the J _sc is 21.59 mA cm⁻² for the device with an AIL-PA HBL. The electron diffusion length L _D is 8.07 μm for the photoanode with AIL-PA I and 7.58 μm for the photoanode with AIL-PA II. (paper)