The potential of hybrid organic-inorganic perovskite solar cells (PSCs) as a next-generation photovoltaic technology has attracted enormous research interest due to their remarkably low cost and outstanding photo-physical properties. Increasing their power conversion efficiency (PCE) using materials which are similarly low-cost as the perovskite layer remains a critical issue for their commercialization; interlayers play important roles in elevating the PCEs of PSCs and the commonly used interlayers used in PSCs are typically orders of magnitude more costly than the perovskite layer itself. Herein, we report the effect of polyelectrolytes on the energy band structure and device characteristics when they are incorporated as electron extraction layers (EELs) of photovoltaics with both N–I–P and P–I–N geometries. To tune and improve device performance, we used cationic nonconjugated polyelectrolytes (NPEs) based on the poly(ethyleneimine) (PEI) backbone with different anions including bromide (Br^-), iodide (I^-), and tetrakis (imidazole) borate (BIm₄^-). This series of NPEs formed electric dipoles at the NPE/metal electrode interfaces; consequently allowing tuning of the energy levels, and work functions (WFs) of the electrodes. Notably, the PCE could be improved from 8.11 to 14.71% in the case of the NIP geometry, or from 7.40 to 13.79% in the case of of the P–I–N geometry using a PEIH⁺BIm₄⁻ interlayer. Ultraviolet photoelectron spectroscope (UPS) results reveal that all of the polyelectrolytes, and particularly PEIH⁺BIm₄⁻ effectively decreased the WFs of the metal electrodes. Interestingly, a tunable dipole was achieved on the conducting surfaces (e.g. both cathode and anode electrodes) modified with electrolytes by simply varying the identity of counterions, as verified by the significantly reduced effective WF. These n-Type electrolytes created Ohmic contacts between the electrodes and the perovskite layer. These findings demonstrate that NPEs are effective EELs for high efficiency PSCs.

混合有机-无机钙钛矿太阳能电池（PSC）作为下一代光伏技术的潜力由于其极低的成本和出色的光物理性能而吸引了巨大的研究兴趣。使用与钙钛矿层类似的低成本材料来提高其功率转换效率（PCE）仍然是其商业化的关键问题；中间层在提升PSC的PCE中起着重要作用，而PSC中常用的中间层通常比钙钛矿层本身的成本高几个数量级。在此，我们报道了聚电解质作为具有N–I–P和P–I–N几何形状的光伏电池的电子提取层（EEL）并入时，对能带结构和器件特性的影响。^- ），碘离子（I ^- ），和四（咪唑）硼酸盐（BIM ₄ ^- ）。这一系列的NPE在NPE /金属电极界面处形成电偶极子。因此，可以调节电极的能级和功函数（WFs）。值得注意的是，PCE可以从8.11在NIP几何结构的情况下提高到14.71％，或从7.40至13.79％在使用PEIH的P-I-N的几何形状的情况下，⁺ BIM ₄ ^-中间层。紫外线光电子能谱（UPS）结果表明，所有的聚电解质，特别PEIH ⁺ BIM ₄ ^-有效地降低了金属电极的WF。有趣的是，通过简单地改变抗衡离子的身份，在用电解质改性的导电表面（例如，阴极和阳极电极）上实现了可调谐偶极子，这已通过有效降低的有效WF进行了验证。这些n型电解质在电极和钙钛矿层之间形成欧姆接触。这些发现表明，NPE是高效PSC的有效EEL。