The coupling and competition of crystallization and phase separation, correlating thermodynamics and kinetics in OPV morphology and performances

Abstract

The active layer morphology transition of organic photovoltaics under non-equilibrium conditions are of vital importance in determining the device power conversion efficiency and stability; however, a general and unified picture on this issue has not been well addressed. Using combined in situ and ex situ morphology characterizations, morphological parameters relating to kinetics and thermodynamics of morphology evolution are extracted and studied in model systems under thermal annealing. The coupling and competition of crystallization and demixing are found to be critical in morphology evolution, phase purification and interfacial orientation. A unified model summarizing different phase diagrams and all possible kinetic routes is proposed. The current observations address the fundamental issues underlying the formation of the complex multi-length scale morphology in bulk heterojunction blends and provide useful morphology optimization guidelines for processing devices with higher efficiency and stability.

Tuning Aggregation Behavior of Polymer Donor viaMolecular‐Weight Control for Achieving 17.1% Efficiency Inverted Polymer Solar Cells

“…GIWAXS was performed to investigate the molecular orientation and packing features of the PM6 with different M w values in solid pure film. [ 47‐51 ] The 2D‐GIWAXS patterns and corresponding scattering profiles are shown in Figures 2a—2e and S4. The π‐π stacking (010) diffraction peaks at 1.68 Å −1 in the out‐of‐plane (OOP) direction became more pronounced with the M w values increasing from 41 to 114 kDa.…”

Unraveling the Mystery of Ternary Organic Solar Cells: A Review on the Influence of Third Component on Structure–Morphology–Performance Relationships

“…At Region III, the accelerated diffusive displacement rate causes micrometer‐sized polymer and fullerene aggregation. [ 122 ] Here, we want to clarify that the temperature‐dependent aggregation discussed is universal to most systems, including fullerene acceptors, [ 124 ] polymer donors, [ 126 ] and NFAs [ 127 ] too. Therefore, most binary BHJs easily fall into the trap of spinodal decomposition and form oversized phases, if not processed carefully.…”

18.4 % Organic Solar Cells Using a High Ionization Energy Self‐Assembled Monolayer as Hole‐Extraction Interlayer

“…In recent years intense research and development efforts have propelled the power conversion efficiency (PCE) of organic photovoltaic (OPV) cells to over 18 %, [1][2][3][4][5] and are now quickly approaching the predicted PCE limit of 20 %. [6,7] To improve the OPVs' performance and stability, research has now been focusing on new bulk-heterojunction (BHJ) systems [8][9][10][11] with an increasing interest in alternative interfacial material technologies. [3,12,13] Although numerous high-performance electron transporting layers (ETLs) have already been developed and deployed in state-of-the-art OPVs (e. g., ZnO, [14] PFN-Br, [15] PNDIT-F3N, [16] PDINO; [17] full chemical names are listed in the Supporting Information), reports on new hole transporting layers (HTLs) remain scarce [2,13,18] with the traditional conductive polymer poly (3,4-ethylenedioxythiophene) : poly(styrene sulfonate) (PEDOT : PSS) retaining its position as the leading HTL system.…”