Inverted Planar Perovskite. Solar Cells with Fill Factor Over 83% via Excess. Organic/Inorganic Halide. Muhammad Jahandar,1,2 Nasir Khan,2,3 Hang Ken Lee ...
High-Performance CH3NH3PbI3 Inverted Planar Perovskite Solar Cells with Fill Factor Over 83% via Excess Organic/Inorganic Halide Muhammad Jahandar,1,2 Nasir Khan,2,3 Hang Ken Lee,1 Sang Kyu Lee,1,2 Won Suk Shin,1,2 Jong-Cheol Lee,1,2 Chang Eun Song*,2,3 and Sang-Jin Moon*,1,2 1Advanced
Materials Division, Korea Research Institute of Chemical Technology (KRICT), 141 Gajeongro, Yuseong, Daejeon 34114, Republic of Korea. 2Advanced Materials and Chemical Engineering, University of Science and Technology (UST), 217 Gajeongro, Yuseong, Daejeon 34113, Republic of Korea. 3Center for Solar Energy Materials, Korea Research Institute of Chemical Technology (KRICT), 141 Gajeongro, Yuseong, Daejeon 34114, Republic of Korea.
Abstract The reduction of charge carrier recombination and intrinsic defect density in organic-inorganic halide perovskite absorber materials is prerequisite to achieving high-performance perovskite solar cells with good efficiency and stability. Here, we fabricated inverted planar perovskite solar cells by incorporation of a small amount of excess organic/inorganic halide (methylammonium iodide (CH3NH3I; MAI), formamidinium iodide (CH(NH2)2I; FAI) and cesium iodide (CsI)) in CH3NH3PbI3 perovskite film. Larger crystalline grains and enhanced crystallinity in CH3NH3PbI3 perovskite films with excess organic/inorganic halide reduce the charge carrier recombination and defect density, leading to enhanced device efficiency (MAI+: 14.49 ± 0.30 %, FAI+: 16.22 ± 0.38 % and CsI+: 17.52 ± 0.56 %) compare to the efficiency of a control MAPbI3 device (MAI: 12.63 ± 0.64 %) and device stability. Especially, the incorporation of a small amount of excess CsI in MAPbI3 perovskite film leads to a highly reproducible fill factor of over 83%, increased open-circuit voltage (from 0.946 V to 1.042 V) and short-circuit current density (from 18.43 mA/cm2 to 20.89 mA/cm2).
Results and discussion
Figure 1. (a) Cross-sectional TEM image of a complete ITO/PEDOT:PSS/Perovskite/PC61BM/LiF/Al inverted planar PeSCs, (b) energy band diagram, and (c) absorption spectra of control and excess OIH incorporated MAPbI3 perovskite film.
Figure 3. (a-d) J-V curves of the control and excess OIH incorporated MAPbI3 inverted planar PeSCs under 1 sun light illumination with respect to scan direction, the reverse and forward scan rate was set to 100 ms per 0.01 V, and (e-h) corresponding external quantum efficiency graph with integrated current density.
Figure 4. (a-d) VOC, JSC, FF, PCE and corresponding RS as a function of light intensity for control and excess OIH incorporated MAPbI3 inverted planar PeSCs. (e-h) current density-voltage characteristics of device with ITO/perovskite/Au configuration for estimating the defect density in perovskite films.
Figure 2. (a-d) FE-SEM images, (e) XRD spectra, and (f-i) 2D GIWAXS patterns of control and excess OIH incorporated MAPbI3 perovskite films. Table 1. Summary of device performance of control and excess OIH incorporated MAPbI3 inverted planar PeSCs.
Perovskite MAI MAI+ FAI+ CsI+
Scan
VOC (V)
JSC (mA/cm2)
FF (%)
η (%)(a)
Reverse
0.946
18.43
77.93
13.58
Forward
0.943
18.28
76.29
13.15
Reverse
0.963
18.73
82.81
14.93
Forward
0.963
18.42
81.45
14.46
Reverse
0.974
20.50
83.99
16.77
Forward
0.980
20.16
83.32
16.45
Reverse
1.042
20.89
83.84
18.24
Forward
1.039
20.66
83.56
17.94
(a)
Best device performance. (b) Average device performance of 30 devices.
Avg. η (%)(b) 12.63 ± 0.64
14.49 ± 0.30
16.22 ± 0.38
17.52 ± 0.56
ACS Appl. Mater. Interfaces, 2017, 9, 35871–35879
Figure 5. Normalized (a) efficiency (ɳ), (b) open-circuit voltage (VOC), (c) current-density (JSC) and (d) fill factor (FF), of control and excess OIH incorporating MAPbI3 inverted planar PeSCs with respect to time.
Conclusion We have demonstrated excess organic/inorganic halide incorporating MAPbI3 PeSCs. The incorporation of small amount of excess MAI, FAI and CsI in MAPbI3 perovskite absorbers forms larger crystalline grains and improves the crystallinity of the perovskite films, which result in reduced charge carrier recombination and defect density. The suppressed charge carrier recombination and reduced defect density in excess OHI incorporating MAPbI3 PeSCs led simultaneously to enhance photovoltaic properties. Consequently, the excess OIH incorporating MAPbI3 PeSCs exhibited greatly improved device efficiency (best PCE = MAI+: 14.93 %, FAI+: 16.77 %, and CsI+: 18.24 %) compared to the efficiency of the control MAPbI3 device (best PCE = 13.58 %) and showed no significant J-V hysteresis under forward and reverse scan directions. Overall, our promising strategy of incorporation of excess OIH in MAPbI3 based perovskite absorbers could enable reproducible manufacturing of large and uniform crystalline perovskite films which would further improve the device performance.
