Poly(3,4‐ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) is widely used as a hole transport layer in inverted perovskite solar cells (PSCs). However, due to the serious interface defects, imperfect energy level arrangement, and low hole transfer rate between PEDOT:PSS and perovskite, the realization of efficient and stable inverted PSCs is hindered. Herein, ionic salt sodium borohydride is used as an interfacial modifier between PEDOT:PSS and MAPbI3−xClx. NaBH4 acts as an anchor to bond Pb2+ to the PEDOT:PSS surface and guides the growth of the perovskite. The champion power conversion efficiency (PCE) of the device based on NaBH4‐PEDOT:PSS reaches 20.21%, which is improved by 27.5% compared with the device based on PEDOT:PSS (15.84%). This PCE is one of the highest in inverted PSCs with PEDOT:PSS as the hole transport layer and MAPbI3−xClx as the active layer. The improved device performance is mainly attributed to the reduced valence band edge of PEDOT:PSS which matches better with the HOMO of MAPbI3−xClx, and the hole transfer rate is increased from 2.65 × 1010 to 3.69 × 1010 s−1. The long‐term stability of the optimized device exceeds 1000 h. This work provides a simple and effective strategy to improve the PCE and stability of inverted PSCs, which is a benefit for future popularization.

Poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been widely used in inverted perovskite solar cells (PSCs) due to its simple preparation process and high stability. However, because of its low conductivity and charge transfer ability, the power conversion efficiency (PCE) of inverted device is poor. To solve this problem, AuCl3 is introduced to modify the interface between the hole transport layer (PEDOT:PSS) and electrode (ITO). The X‐ray photoelectron spectroscopy  (XPS) spectra of PEDOT:PSS confirms that the PSS chains are reduced and the conductivity are increased after AuCl3 doping. Moreover, AuCl3‐modified PEDOT:PSS is beneficial to guide crystal growth and to improve the grain size, crystallinity, and water contact angle of perovskite films. Meanwhile, the defects of PEDOT:PSS/perovskite interface are effectively passivated, which suppresses the nonradiative recombination. The hole extraction efficiency is improved from 8.88× to 1.31× s−1. As a result, the short‐current density (Jsc) and fill factor (FF) are improved, which leads to a champion device with PCE up to 18.08%, much higher than 16.03% of pristine one. The unencapsulated device remains 80% of the initial efficiency after 4 weeks under 45 ± 5% humidity. The results provide a new strategy for synergistically enhancing the efficiency and stability of PSCs by interfacial modification and doping.

Nickel oxide (NiO x ) is one of the most widely used inorganic hole transport materials for inverted perovskite solar cells (PSCs), which has the advantages of low cost, easy preparation, and good stability. However, the energy‐level mismatch and interfacial redox reactions at the NiO x /perovskite interface limit the performance of NiO x ‐based PSCs. Herein, triphenylamine‐2,1,3‐benzothiadiazole‐triphenylamine (TBT) small‐molecule material is first used as an interfacial modification layer between NiO x and perovskite. The deposition of TBT on NiO x helps to hinder the contact between NiO x and perovskite, improves the electrical conductivity, passivates interfacial defects, and inhibits the recombination of interfacial carriers. TBT makes the valance band top energy level of NiO x better match that of perovskite and promotes the hole transfer at NiO x /perovskite interface, and the hole transfer rate increases from 2.19 × 1010 to 4.12 × 1010 s−1. The TBT‐based device obtains a champion power conversion efficiency (PCE) of 21.84%, much higher than the control device (18.62%). Furthermore, the optimized device which is conserved in 30 ± 5% relative humidity and 25 °C environments more than 1000 h retains 90% of the initial efficiency. A effective strategy to improve the PCE and stability of NiO x ‐based PSCs is provided.

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