Environmentally Printing Efficient Organic Tandem Solar Cells with High Fill Factors: A Guideline Towards 20% Power Conversion Efficiency

Abstract

The tandem concept involves stacking two or more cells with complementary absorption spectra in series or parallel connection, harvesting photons at the highest possible potential. It is strongly suggested that the roll‐to‐roll production of organic solar cells will employ the tandem concept to enhance the power conversion efficiency (PCE). However, due to the undeveloped deposition techniques, the challenges in ink formulation as well as the lack of commercially available high performance active materials, roll‐to‐roll fabrication of highly efficient organic tandem solar cells currently presents a major challenge. The reported high PCE values from lab‐scale spin‐coated devices are, of course, representative, but not helpful for commercialization. Here, organic tandem solar cells with exceptionally high fill factors and PCE values of 7.66% (on glass) and 5.56% (on flexible substrate), which are the highest values for the solution‐processed tandem solar cells fabricated by a mass‐production compatible coating technique under ambient conditions, are demonstrated. To predict the highest possible performance of tandem solar cells, optical simulation based on experimentally feasible values is performed. A maximum PCE of 21% is theoretically achievable for an organic tandem solar cell based on the optimized bandgaps and achieved fill factors.

Fully printed organic tandem solar cells using solution-processed silver nanowires and opaque silver as charge collecting electrodes

“…Owing to their promising air-processing compatibility, two spectrally complementary polymer donors, GEN-2 and pDPP5T-2, which have been intensively studied previously, were employed as photoactive materials. 11,14 The absorption spectra of the two active layers (donor blended with acceptor PCBM) are shown in Fig. S2 (ESI †).…”

“…[10][11][12][13] Theoretical calculations indicate that double-junction tandem OSCs hold the potential to reach PCE of 420%, showing an improvement of B40% compared to the optimized single cells. 14,15 Benefitting from recently developed efficient charge recombination layers and high-performance low band-gap materials, several research groups have reported tandem OSCs with PCEs of over 10%, which is considered to be the benchmark for practical applications.…”

Air-processed organic tandem solar cells on glass: toward competitive operating lifetimes

“…9 Recently, triple-junction devices with 11.5% and 12% conversion efficiency have been announced by Yang Yang's group 10 and by Heliatek, 11 respectively, which clearly states the potential of this technology.…”

A universal method to form the equivalent ohmic contact for efficient solution-processed organic tandem solar cells

“…This concept addresses both losses: the J sc related absorption losses as well as the V oc related thermalization losses. In the last few years, a number of organic tandem solar cells with high efficiencies were reported, 8,[15][16][17][18][19][20][21][22] and the efficiency roadmap for tandem cells is clearly pointing towards the predicted 15%. 23 To realize high performance organic tandem solar cells, an efficient and reliable intermediate layer (IML) is required, which is typically designed from a series-connected sequence of a holetransporting layer (HTL) and an electron-transporting layer (ETL).…”