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鈣鈦礦太陽能電池(PSCs)因其高效率和低成本的優(yōu)勢獲得廣泛關(guān)注與研究。然而，鈣鈦礦在成核和晶體生長的過程中不可避免地會形成缺陷，被認(rèn)為是制約器件光伏性能和穩(wěn)定性的重要原因。在近幾年的研究中，有機鹵化銨鹽常被用于鈍化鈣鈦礦的表面缺陷，其作用機理大致可分為分子鈍化機制和LD/3D異質(zhì)結(jié)機制。通過化學(xué)反應(yīng)形成LD/3D異質(zhì)結(jié)構(gòu)不僅可以鈍化點缺陷，還可以通過消除不需要的表面晶相和修復(fù)針孔、裂紋等形態(tài)缺陷來重建3D鈣鈦礦表面，被認(rèn)為是一種比分子鈍化更強大的界面工程方法。
近日，華南農(nóng)業(yè)大學(xué)饒華商&鐘新華團隊在碳基無機鈣鈦礦太陽電池上取得重要進(jìn)展，研究成果以“1D Choline-PbI3-Based Heterostructure Boosts Efficiency and Stability of CsPbI3 Perovskite Solar Cells”為題發(fā)表在國際 期刊Angewandte Chemie（DOI：10.1002/anie.202303486）上。華南農(nóng)業(yè)大學(xué)張鍵鑫博士生為*一作者，饒華商副教授為通訊作者。
Figure 1. a) XRD patterns of CsPbI3 films without (w/o) and with ChI treatment. b) Temporal evolution of the suspicious peaks from XRD with ChI treatment under ambient atmosphere (RH = ~80%). c) XRD patterns of ChI-PbI2 crystal powder and simulated ChPbI3. d) Schematic crystal structure of hexagonal ChPbI3. e) ToF-SIMS depth profile of Ch+, Pb2+, I− and Ti4+ in CsPbI3/TiO2 film with ChI treatment.
該團隊通過詳細(xì)的相結(jié)構(gòu)演變追蹤和單晶解析發(fā)現(xiàn)，ChI處理CsPbI3表面的過程中會原在表面和晶界處原位生成1D結(jié)構(gòu)的ChPbI3（Figure 1）。1D ChPbI3的原位生成與原始的3D CsPbI3形成1D/3D異質(zhì)結(jié)構(gòu)，通過進(jìn)一步的光電測試（穩(wěn)態(tài)熒光和熒光衰減）證明了1D/3D異質(zhì)結(jié)構(gòu)能夠有效地的鈍化薄膜缺陷，顯著地提高了光致發(fā)光壽命，抑制非輻射復(fù)合損失（Figure 2）。
Figure 2. a) Evolution of XRD patterns of CsPbI3 films with ChI treatment over time at room temperature (25 °C). b) XRD patterns of CsPbI3 films without and with ChI treatment annealed at different temperature for 15 min. c) PL spectra for CsPbI3 films with ChI treatment over time at room temperature. d) PL spectra for 3D-film and 1D/3D-film. e) PL delay curves of 3D-film and 1D/3D-film.
由于1D ChPbI3本身超疏水能力，1D/3D異質(zhì)結(jié)的形成極大地增強了鈣鈦礦薄膜的水分穩(wěn)定性。另外，1D ChPbI3優(yōu)異的化學(xué)惰性和在其形成過程中修復(fù)不需要的δ-CsPbI3缺陷，抑制壞點的擴散，可以顯著增強CsPbI3薄膜的穩(wěn)定性。（Figure 3）
Figure 3. a) Photos showing color changes of 3D- and 1D/3D-film at RH=40~50% over time. Evolution of XRD patterns of b) 3D- and c) 1D/3D-film at RH=40~50% over time. The color bar on the left side represents time, and the color bar on the right side indicates the XRD intensity. d) XRD patterns of ChPbI3 crystals before and after soaking in water for 6 h. e) XRD patterns of 3D-film containing δ-CsPbI3 blemish before and after ChI treatment. f) Schematic illustration of inhibition of δ-phase by ChI treatment on CsPbI3 surface.
鑒于1D/3D結(jié)構(gòu)的構(gòu)建對CsPbI3薄膜缺陷態(tài)鈍化和穩(wěn)定性提高方面的作用，組裝的 CsPbI3 C-PSC的穩(wěn)定性顯著增強，器件的光電轉(zhuǎn)換效率從原始的13.69%提升至18.05%并獲得了17.8%的認(rèn)證效率，這是目前無空穴傳輸材料的碳基無機PSCs新的效率記錄（Figure 4d）。進(jìn)一步探究了Voc對入射光強度的依賴性，Mott-Schottky等測試，證明了ChI處理可以通過構(gòu)建1D ChPbI3/3D CsPbI3異質(zhì)結(jié)構(gòu)，有效抑制器件中的非輻射復(fù)合，從而顯著提高Voc。（Figure 4）
Figure 4. a) Statistic distribution of Voc and PCE of C-PSCs based on various concentrations of ChI solution based on 30 individual devices. b) Forward and reverse J–V curves and c) SPO curves of 3D- and 1D/3D-cells. d) Summarized PCE values of reported inorganic C-PSCs. e) Voc dependence on light intensities and f) Mott–Schottky plots of 3D- and 1D/3D-cells.
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