Fig. 1. (Color online) Transparency and sheet resistance of the transparent conducting electrodes (reproduced with copyright permission from SPIE publisher)^[6].

Fig. 2. (Color online) (a) Photographs of the large-area flexible OSCs. (b) J–V characteristics and (c) EQE spectra of the large-area flexible solar cells with PET/Ag/Cu grid electrodes. (d) J–V characteristics and (e) EQE spectra of the large-area flexible solar cells with PET/ITO electrodes (reproduced with copyright permission from Wiley-VCH)^[16].

Fig. 3. (Color online) (a) Sketch of spin coating and slot-die coating. (b) The small-area rigid device and large-area flexible device. (c) The chemical structures of PTB7-Th, PC₇₁BM, and COi8DFIC. (d) Optical microscopy and SEM images of the PET/silver-grid substrate. (e) Comparison of this work with reported PCEs for flexible devices made by slot-die coating (reproduced with copyright permission from Wiley-VCH)^[4].

Fig. 4. (Color online) (a) Schematic diagram for the high-speed gravure printing process used to print silver nanowire electrodes. (b) Efficiency distribution diagram for the devices with PET/AgNWs-GV, PET/AgNWs-SP, and glass/ITO electrodes (reproduced with copyright permission from Wiley-VCH)^[3].

Fig. 5. (Color online) The PCEs for small-area OSCs^{[1, 2, 28–35]}, large-area OSCs (>1 cm²)^{[3, 10, 11, 16, 36–41]}, and flexible OSC modules^{[4, 27, 37, 38, 42–47]}.

Table 1. The performance data for large-area flexible OSCs (> 1 cm²) (Fig. 5).

Table 2. The performance data for flexible OSC modules (Fig. 5).