Charged defects at the surface of the organic–inorganic perovskite active layer are detrimental to solar cells due to exacerbated charge carrier recombination. Here we show that charged surface defects can be benign after passivation and further exploited for reconfiguration of interfacial energy band structure. Based on the electrostatic interaction between oppositely charged ions, Lewis-acid-featured fullerene skeleton after iodide ionization (PCBB-3N-3I) not only efficiently passivates positively charged surface defects but also assembles on top of the perovskite active layer with preferred orientation. Consequently, PCBB-3N-3I with a strong molecular electric dipole forms a dipole interlayer to reconfigure interfacial energy band structure, leading to enhanced built-in potential and charge collection. As a result, inverted structure planar heterojunction perovskite solar cells exhibit the promising power conversion efficiency of 21.1% and robust ambient stability. This work opens up a new window to boost perovskite solar cells via rational exploitation of charged defects beyond passivation.

of semitransparent organic solar cells (ST-OSCs) with transparent facilities, such as building windows, automobile glass, and greenhouse rooftops, is of particular interest, since it opens up the prospect of employing the facade for solar-power generation rather than simply employing shadowing and visual functions. [7][8][9][10][11][12] Toward this purpose, ST-OSCs need to generate significant power while still maintaining good transparency and neutral-color perception, which can display a vivid picture when looking through ST-OSCs. [13,14] However, the current performance of ST-OSCs is much lower than their opaque counterparts due to their inherent trade-off between photocurrent and average visible transmittance (AVT) in the range of 380-780 nm. Even worse, these ST-OSCs generally display various colors, making it more difficult to realize high-performance ST-OSCs with promising AVT and neutral color simultaneously. To address the above issues, many efforts have been devoted to the following aspects: (1) developing high-conductivity and high-transparency electrodes to reduce the visible-light reflectance/absorption and contact resistance [15,16] ; (2) synthesizing a nonfullerene acceptor-based photoactive layer with low energy losses and strong near-infrared (NIR) absorption but weak visible absorption to simultaneously increase AVT and power conversion efficiency (PCE) [17][18][19][20][21] ; and (3) incorporating optical engineering to enhance absorption and tuning color conception. [22][23][24][25][26] Based on the above strategies, as shown in Figure 1a, ST-OSCs with promising PCEs of 8%-10% and AVT of over 20% were successfully constructed. [19,[27][28][29] However, the transmitted light still showed strong color bias because of the inhomogeneous device transmittance spectra.To achieve high color-fidelity ST-OSCs for building-integrated photovoltaics application, the light passing through ST-OSCs should maintain the initial component and relative intensity. In other words, the transmittance spectra with flattened, high-transparency, and horizontal characteristics in the visible region can enable neutral-color ST-OSCs. Generally, the color conception of ST-OSCs can be quantified by a color-rendering index (CRI) ranging from 0 to 100 and the color coordinates (x, y) on the Commission Internationale de L'Eclairage (CIE, in French) 1931 color space, where a high CRI value and color coordinates close to AM1.5G (0.35, 0.34) represent neutral-color ST-OSCs. [22,30] Colsmann and co-workers [31] added a red absorbing dye into a top transparent polymeric electrode to compensate for the missing Neutral-colored semitransparent organic solar cells (ST-OSCs) have attracted considerable attention owing to their unique application in no-visual-obstacle building-integrated photovoltaics. Toward this promising potential application, a synergistic effect is first proposed by employing a dielectric mirror and ternary photoactive layer with near-infrared absorption to tune the color perception as well as ST-OSC performance preci...

solution-processing opens an avenue toward flexibility, simple device fabrication, versatility of interface engineering, and feasibility of multijunction solar cells. [1,2] The rapidly developed planar p-i-n pero-SCs promote its power conversion efficiency (PCE) exceeding 21%. [3][4][5] Among the highperformance devices, [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) is by far predominantly used for the electron transport layer (ETL) in planar p-i-n pero-SCs owing to its multifunctionality, including trap-states passivation and efficient electron extracting ability. [6][7][8] Nevertheless, some inferior properties, such as insufficient coverage on perovskite film, [9] energy disorder, [10] and ineffective passivation on the under-coordinated Pb 2+ ions defects of perovskite surface, [5] still hamper further enhancement of the PCE and stability of the PCBM-based pero-SCs.As for the conventional PCBM ETL grown on perovskite film, because of its discontinuous and aggregated nature, the water molecules in ambient atmosphere can easily permeate it then diffuse into the perovskite film. [9,11] This process is likely to form a hydrate perovskite phase that would accelerate the decomposition of CH 3 NH 3 PbI 3 (MAPbI 3 ) crystal lattice. [12] The resulting decomposition products, such as HI and I 2 , can further diffuse and penetrate PCBM film to react with Ag or Al metal electrode forming an Ag-I or Al-I insulating layer under the metal electrode, thus leading to further degradation of the pero-SCs. [11,13] In order to address this issue, an encapsulating strategy was employed. For example, thick PCBM film and bilayer structure, such as PCBM/metal oxide, [14] PCBM/PS, [15] and PEAI/PCBM, [16] can effectively reduce the discontinuity or enhance the hydrophobicity of PCBM films for preventing moisture permeation. However, the device performance was limited, due to the mismatched energy level/electron mobility between bilayers, and the increased charge recombination in thick PCBM film or bilayers. Therefore, extensive work toward designing new fullerene derivatives with good film-forming ability, [17] high electron mobility, [18] and water-resistant ability [19] have been conducted to replace PCBM as ETL, but have rarely shown both high efficiencies and high stabilities in the p-i-n pero-SCs.On the other hand, recent studies have clearly revealed that various types of defects, including vacancies, interstitials, and antisites, existing at the surface and grain boundaries of The poor long-term stability of organic-inorganic hybrid halide perovskite solar cells (pero-SCs) remains a big challenge for their commercialization.Although strategies such as encapsulation, doping, and passivation have been reported, there remains a lack of understanding of the water resistance and thermal stability of pero-SCs. A fullerene derivative, [6,6]-phenyl-C 61 -butyric acid-N,N-dimethyl-3-(2-thienyl)propanam ester (PCBB-S-N) containing a functional sulfur atom and C 60, is synthesized and employed as electron transporting layer (ETL)/i...

In p‐i‐n planar perovskite solar cells (pero‐SCs) based on methylammonium lead iodide (MAPbI3) perovskite, high‐quality MAPbI3 film, perfect interfacial band alignment and efficient charge extracting ability are critical for high photovoltaic performance. In this work, a hydrophilic fullerene derivative [6,6]‐phenyl‐C61‐butyric acid‐(3,4,5‐tris(2‐(2‐(2‐methoxyethoxy)ethoxy)ethoxy)phenyl)methanol ester (PCBB‐OEG) is introduced as additive in the methylammonium iodide precursor solution in the preparation of MAPbI3 perovskite film by two‐step sequential deposition method, and obtained a top‐down gradient distribution with an ultrathin top layer of PCBB‐OEG. Meanwhile, a high‐quality perovskite film with high crystallinity, less trap‐states, and dense‐grained uniform morphology can well grow on both hydrophilic (poly(3,4‐ethylenedioxythiophene)/poly(styrenesulfonic acid)) and hydrophobic (polytriarylamine, PTAA) hole transport layers. When the PCBB‐OEG‐containing perovskite film (pero‐0.1) is prepared in a p‐i‐n planar pero‐SC with the configuration of ITO/PTAA/pero‐0.1/[6,6]‐phenyl‐C61‐butyric acid methyl ester/Al, the device delivers a promising power conversion efficiency (PCE) of 20.2% without hysteresis, which is one of the few PCE over 20% for the p‐i‐n planar pero‐SCs. Importantly, the pero‐0.1‐based device shows an excellent stability that can retain 98.4% of its initial PCE after being exposed for 300 h under ambient atmosphere with a high humidity, and the flexible pero‐SCs based on pero‐0.1 also demonstrate a promising PCE of 18.1%.

The power conversion efficiency (PCE) of planar p–i–n perovskite solar cells (pero‐SCs) is commonly lower than that of the n–i–p pero‐SCs, due to the severe nonradiative recombination stemming from the more p‐type perovskite with prevailing electron traps. Here, two n‐type organic molecules, DMBI‐2‐Th and DMBI‐2‐Th‐I, with hydrogen‐transfer properties for the doping of bulk perovskite aimed at regulating its electronic states are synthesized. The generated radicals in these n‐type dopants with high‐lying singly occupied molecular orbitals enable easy transfer of the thermally activated electrons to the MAPbI3 perovskite for the realization of n‐doped perovskites. The n‐doping degree could be further enhanced by using the iodine ionized dopant DMBI‐2‐Th‐I. The doping effect could reduce the electron trap density, increase the electron concentration of the bulk perovskite, and simultaneously improve the surface electronic contact. When the DMBI‐2‐Th‐I‐doped perovskite is used in planar p–i–n pero‐SCs, the nonradiative recombination is significantly suppressed. As a result, the photovoltaic performance improved significantly, as evidenced by an excellent PCE of 20.90% and a robust ambient stability even under high relative humidity. To the best of the knowledge, this work represents the first example where organic n‐type dopants are used to tune the electronic states of a bulk perovskite film for efficient planar p–i–n pero‐SCs.