Ternary Blend Organic Solar Cells: Understanding the Morphology from Recent Progress

Abstract

layer with binary components, where the spontaneous phase separation of the electron donor (D) and electron acceptor (A) provide sufficient D/A interfaces for charge dissociation and continuous network for charge transport. [19,20] In principle, a strong absorbance with a broad absorption band of the photoactive layer is a prerequisite to maximize the harvesting of photons, thereby realizing high photocurrent of the OSC device. [21] In the early period, fullerene derivatives dominated the acceptors, which have low absorption ability, the donor materials contributed mainly to the light harvesting. However, common organic semiconductors intrinsically possess narrow absorption window (the full width at half maximum of the absorption spectrum is about 100-200 nm), which makes it very difficult to realize a broad plateau absorption coverage. [19][20][21][22] Therefore, the device performances were severely restrained to ≈12% for the fullerene-based OSCs. [23][24][25][26] Over the past few years, nonfullerene acceptors (NFAs) have witnessed rapid progress owing to their facile synthesis, easily tunable optoelectronic properties, and strong absorption even reaching the nearinfrared (NIR) region. [3] The largely extended absorption range was realized by pairing low bandgap (LBG) NFAs with the wide bandgap (WBG) polymer donors, thus significantly improving the short current density (J sc ) and PCEs. [5][6][7][8][9][10][11][12][13][14][15] However, its further improvement still remains a formidable challenge due to the almost saturated design toolbox of building blocks for brand new donor/acceptor materials and the insufficient light absorption coverage by binary blends. [27] To make the most of the vast existing pool of semiconductors with various bandgaps and overcome the absorption limitations, tandem devices and ternary blend devices were developed. Tandem OSCs improve the light absorption ability by vertical stacking multiple single-junction cells with complementary absorption. [28] By harvesting both high and low energy photons in the separated subcells, tandem OSCs are able to diminish thermalization loss of photonic energy and overcome the Shockley-Queisser (S-Q) limit. [29] The rapid progress in NFAs has boosted the PCE of tandem OSCs approaching 20%. [14] However, the fabrication of tandem OSCs involves complicated multilayer deposition with serious technical challenges, which may limit their industrialization prospect. Alternatively, the ternary blend organic solar cells (TB-OSCs) strike a good balance between light-harvesting enhancement and device fabrication simplicity by directly Ternary blend organic solar cells (TB-OSCs) incorporating multiple donor and/or acceptor materials into the active layer have emerged as a promising strategy to simultaneously improve the overall device parameters for realizing higher performances than binary devices. Whereas introducing multiple materials also results in a more complicated morphology than their binary blend counterparts. Understanding the morphology is crucially im...

Manipulating the Intermolecular Interactions through Side Chain Engineering and Unilateral π‐Bridge Strategy for Efficient Small Molecular Photovoltaic Acceptor

“…, where γ represents the surface tension and K is a constant (K = 1.16 × 10 5 m −1/2 ), the χ could be experimentally calculated. [53] It is evident that the closer the γ of donor and acceptor, the smaller the χ is, and better the miscibility will be, and vice versa. The γ values could be obtained through the contact angle (CAs) measurements based on two separate liquids.…”

Realizing 19.05% Efficiency Polymer Solar Cells by Progressively Improving Charge Extraction and Suppressing Charge Recombination

“…Solution-processable polymer solar cells (PSCs) have received considerable attention, owing to their unique features of light weight, mechanical flexibility, semitransparency, and ease of fabrication for large-area devices. [1,2] Over the past decades, the utmost endeavors have been devoted to modulating the structural and optoelectronic properties by designing new organic semiconductors, [3][4][5] controlling the morphology of photoactive layer via additives and various post-treatments, [6][7][8] maximizing the harvest of light by using ternary or tandem devices, [9][10][11][12][13][14][15][16][17] improving the extraction of electrons and holes by interfacial modification. [18][19][20] With these efforts, PSCs have witnessed rapid progress, the cutting-edge PSCs have delivered over 18% power conversion efficiencies (PCEs) (Table S1, Supporting Information), [7,8,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] and there still has much space to further improvement.…”

Hole/Electron Transporting Materials for Nonfullerene Organic Solar Cells

“…[1b,2] The enormous research efforts dedicated to developing novel photosensitive materials (including polymer and small molecules) and optimizing the bulk heterojunction (BHJ) morphology of the active layer have made a continuous progress of OSCs. [2][3] Particularly, the recent prevailing nonfullerene acceptors (NFAs) matching those highly efficient polymer donors have shown great advantages in extending the light absorption range for a high short-circuit current density (J sc ) and reducing energy loss for a high open-circuit voltage (V oc ). [4] For these reasons, NFA-based OSCs (NF-OSCs) have become the workhorses in this field, and state-of-the-art NF-OSCs have reached the milestone power conversion efficiencies (PCEs) of over 18 %, [3g,5] which are comparable to the commercial silicon-based solar cells.…”