Controlling the perovskite morphology and defects at the buried perovskite-substrate interface is challenging for inverted perovskite solar cells. In this work, we report an amphiphilic molecular hole transporter, (2-(4-(bis(4-methoxyphenyl)amino)phenyl)-1-cyanovinyl)phosphonic acid, that features a multifunctional cyanovinyl phosphonic acid group and forms a superwetting underlayer for perovskite deposition, which enables high-quality perovskite films with minimized defects at the buried interface. The resulting perovskite film has a photoluminescence quantum yield of 17% and a Shockley-Read-Hall lifetime of nearly 7 microseconds and achieved a certified power conversion efficiency (PCE) of 25.4% with an open-circuit voltage of 1.21 volts and a fill factor of 84.7%. In addition, 1–square centimeter cells and 10–square centimeter minimodules show PCEs of 23.4 and 22.0%, respectively. Encapsulated modules exhibited high stability under both operational and damp heat test conditions.
Formamidinium lead iodide (FAPbI 3 ) has endowed power conversion efficiencies (PCEs) up to 25.5% in regular-structured perovskite solar cells (PSCs) because of its optimal bandgap and enhanced thermal stability. However, the performance of FAPbI 3 -based inverted-structured PSCs is unsatisfactory. Herein, four kinds of commonly used hole transport materials (HTMs) are selected, including PEDOT:PSS, PTAA, NiOx, and MeO-2PACz, to study their impact on the methylamine chloride (MACl)-assisted one-step deposition of FAPbI 3 films. It is found that MeO-2PACz is the optimal substrate for stabilizing black-phase FAPbI 3 and the corresponding inverted-structured PSCs show the best photovoltaic performance. Nonetheless, the PCE is restricted by low open-circuit voltage (V OC ) due to non-radiative recombination caused by MACl residues. Therefore, homologous PbI 2 in situ passivation is implemented to passivate defects at grain boundaries. The addition of excess PbI 2 in precursor solution remarkably decreases charge trap densities and elongates carrier lifetimes. As a result, the optimized device achieves an impressive PCE of 22.13%, which is the highest efficiency of FAPbI 3 based on inverted-structured PSCs. Moreover, the best device exhibits free hysteresis and excellent long-term stability, maintaining 92% of the initial PCEs after 800 h aging under ambient conditions.
Incorporating non-aqueous hole-transporting materials (HTMs) to replace the widely used PEDOT:PSS is favorable for improving the stability of tin-lead perovskite solar cells (Sn-Pb PSCs). Herein, hexaazatrinaphthylene (HATNA) is found to be a promising HTM building block for Sn-Pb PSCs. By introducing triphenylamine (TPA) and methoxy-triphenylamine into the HATNA core, molecular energy levels and surface wettability can be well regulated, and a high hole mobility and thermal stability can be maintained. Moreover, a homogeneous Sn-Pb perovskite film with low Sn4+ contents and vertically orientated grains can be prepared on the substrate TPA-HATNA. Compared with PEDOT:PSS, the optimal TPA-HATNA-based methylammonium-free device enables a 70 mV increase in V OC, delivering a remarkable PCE exceeding 18% (certified 16.4%). Impressively, the TPA-HATNA-based devices without encapsulation retain 90% efficiency after aging for 600 min under maximum-power-point tracking. Our work provides alternative HTMs for boosting the performance of Sn-Pb PSCs.
Halide diffusion across the charge‐transporting layer followed by a reaction with metal electrode represents a critical factor limiting the long‐term stability of perovskite solar cells (PSCs). In this work, a supramolecular strategy with surface anion complexation is reported for enhancing the light and thermal stability of perovskite films, as well as devices. Calix[4]pyrrole (C[4]P) is demonstrated as a unique anion‐binding agent for stabilizing the structure of perovskite by anchoring surface halides, which increases the activation energy for halide migration, thus effectively suppressing the halide–metal electrode reactions. The C[4]P‐stabilized perovskite films preserve their initial morphology after ageing at 85 °C or under 1 sun illumination in humid air over 50 h, significantly outperforming the control samples. This strategy radically tackles the halide outward‐diffusion issue without sacrificing charge extraction. Inverted‐structured PSCs based on C[4]P modified formamidinium–cesium perovskite exhibit a champion power conversion efficiency of over 23%. The lifespans of unsealed PSCs are unprecedentedly prolonged from dozens of hours to over 2000 h under operation (ISOS‐L‐1) and 85 °C ageing (ISOS‐D‐2). When subjected to a harsher protocol of ISOS‐L‐2 with both light and thermal stresses, the C[4]P‐based PSCs maintain 87% of original efficiency after ageing for 500 h.
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