Photoconductive Charge Transfer Complexes as Charge Transport Layers for High Performance Inverted Perovskite Solar Cells

Abstract

Charge transport layers (CTLs) are critical for achieving high power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). Herein, the p-type bulk heterojunction (p-BHJ, i.e., PCBM doped PTAA) and n-type BHJ (n-BHJ, i.e., PBDTTT-C-T doped PCBM) charge transfer complexes are employed as hole and electron transport layers, respectively, to fabricate inverted PSCs. The photo-induced charge transfer between p-type and n-type organic semiconductors in the BHJ layers provides extra photoconductivity for enhanced charge transport and quasi-Fermi level splitting, hence enhancing the fill factor and open-circuit voltage of PSCs. The p-BHJ layer helps to improve the crystallinity and light absorption of perovskite, whilst the n-BHJ layer provides extra light absorption and charge generation to boost the short-circuit current. The combination of p-BHJ and n-BHJ CTLs in Cs 0.05 (FA 0.92 MA 0.08 ) 0.95 Pb (I 0.92 Br 0.08 ) 3 based inverted PSCs synergistically enhances the PCE from 18.3% to 22.6% with superior operational and thermal stabilities, and showing a negligible dependence on the thickness of these BHJ CTLs. Density functional theory simulations show that the formation energy of BHJ complex is critical in determining the doping effect and the ultimate performance enhancement of PSCs.

Niobium‐Carbide MXene Modified Hybrid Hole Transport Layer Enabling High‐Performance Organic Solar Cells Over 19%

“…[6][7][8][9][10] In addition to the advances in synthesizing novel active materials, high-performance OSCs can be realized by improving the optoelectrical properties of the charge transport layers (CTL) which play an important role in energy-level alignment, charge collection, and morphology control. [11][12][13][14][15] Among the commonly used materials as CTL, poly (3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) received particular attention as the state-of-art hole transport material because of its excellent transparency, solution processability, and appropriate work function (WF). [16,17] However, PEDOT:PSS also displays some disadvantages such as the high acidity and the low electrical conductivity owing to the presence of insulated PSS, leading to electrical loss and long-term degradation in device performance.…”

Annealing-Free SnO2 Layers for Improved Fill Factor of Perovskite Solar Cells

“…As shown in Figure 3c,d, the surface potential of the NPE-SnO 2 film is higher than that of the A-SnO 2 film, indicating that the Fermi level of the NPE-SnO 2 film is approaching the bottom of the conduction band, which is consistent with the UPS (the crude-data curves of KPFM are presented in Figure S6c). 30 Steady-state photoluminescence (PL) and time-resolved PL (TRPL) were adopted to examine the charge transfer properties with the structure of ITO/ETL/perovskite. 31 As shown in Figure 4a, the constant PL emission peak suggests that there is no effect of A-SnO 2 and NPE-SnO 2 on the perovskite composition.…”

A Smart Way to Prepare Solution‐Processed and Annealing‐free PCBM Electron Transporting Layer for Perovskite Solar Cells

“…Although the solubility and dissolution rate of PC 61 BM in perovskite precursor solution is not high, PC 61 BM as the ETL in n-i-p-type devices is quite a thin layer, therefore, depositing perovskite precursor solution will inevitably destroy or partially destroy the beneath PC 61 BM layer. [33] As a result, devices fabricated directly based on the PC 61 BM ETL usually exhibit low efficiency and poor reproducibility. To protect the PC 61 BM ETL, the strategy of presaturating the perovskite precursor solution with PC 61 BM is worth trying.…”

“…On the other hand, the pre-saturated PC 61 BM in perovskite could effectively passivate defects at the perovskite grain boundaries, thus enhancing charge transporting and reducing charge recombination, as reported previously. [33][34][35] As a result, conventional PSC fabricated with PC 61 BM as the bottom ETL and meanwhile containing saturated PC 61 BM in the perovskite precursor (denoted as the improved device), shows a high power conversion efficiency (PCE) of 20.85%, with a high open-circuit voltage (V oc ) of 1124 mV, a short-circuit current density (J sc ) of 22.77 mA cm -2 , and a fill factor (FF) of 81.47%. For comparison, control device was fabricated, in which only pristine PC 61 BM was used as the ETM, and PC 61 BM was not added into the perovskite precursor solution.…”