Low Threshold Amplified Spontaneous Emission from Efficient Energy Transfer in Blends of Conjugated Polymers

Abstract

The concentration dependence of amplified spontaneous emission (ASE) and lasing characteristics in the blend of blue emitting poly(9,9-dioctylfluorene) (PFO) and ladder-type poly(indenofluorene) (2LF-BT) has been reported. A methodology for selecting the optimal blend composition in the blend systems is developed to enhance the optical gain characteristics. It is observed that as the PFO concentration increases, the ASE threshold rapidly decreases from the original 65 to 4.8 μJ cm −2 (30% PFO). Subsequently, the ASE threshold value gradually increases by further increasing the PFO concentration. Under this circumstance, 30% PFO is the optimized concentration for PFO/2LF-BT binary blend films with the maximum gain of 93 cm −1 and superior ASE stability upon annealing. According to atomic force microscopy (AFM) images, morphologies of blend samples are smooth with no phase separation regardless of the PFO concentration, demonstrating attractive advantages over other previously reported blend systems which usually suffer from phase separation. Distributed feedback (DFB) lasers based on the blend film with 30% PFO have low thresholds of 4.85 μJ cm −2 (0.97 kW cm −2 ) . These optical and gain characteristics render the conjugated polymer blends attractive materials for organic lasing. It is worthwhile to mention that the strategy for judicious selection of the blend systems which comprise conjugated polymers with similar backbone structures has made a great contribution to the improvement of organic lasing performance in terms of ASE properties and optical gains.

Gain Bandwidth Engineering in Polymer Blends for Full‐Color‐Tunable Lasers

“…As a point of comparison, the measured ASE thresholds obtained here are among the lowest values reported in dendritic starbursts, [ 42–45 ] polymers, [ 46,47 ] and guest–host gain systems under nanosecond pulse excitation. [ 36,37,48–50 ] Intriguingly, the peaks of green amplification in the blended polymers do not show any shift with respect to the blending ratio (Figure 2e). However, the peaks of yellow and red amplification undergo bathochromic shifts with increasing dopant concentration in BEHP‐PPV:MEH‐PPV blend system by varying from 562 to 577 nm and from 600 to 618 nm, respectively.…”

Benzoxazole-Based Hybridized Local and Charge-Transfer Deep-Blue Emitters for Solution-Processable Organic Light-Emitting Diodes and the In fluences of Hexahydrophthalimido

“…Developing light-emitting charge-transfer materials with high solid-state photoluminescence quantum yields (PLQYs) is of great interest because of their potential applications in organic light-emitting devices (OLEDs) and organic lasing. − Hybrid localized charge-transfer (HLCT) materials that can theoretically achieve 100% IQE through a “hot exciton” channel have attracted extensive attention in recent years owing to their high luminescence efficiency, good color purity, and suppressing low-efficiency roll-off caused by accumulation of triplet excitons . It has been considered a promising strategy to achieve high-efficiency device performance, especially in deep-blue OLEDs. − The HLCT materials highlight the reverse intersystem crossing (hRISC) from the high-lying triplet excitation states (T n ) to the singlet excitation state (S 1 or S 2 ), where a small energy gap between Tn and the singlet state formed a fast process within several nanoseconds, while a large energy gap between T n and T 1 states prevented interconversion.…”

Effect of structural modifications on the spectral and lasing characteristics of truxene-cored starbursts with/without diphenylamine end-cappers

“…Organic semiconductors based on π-conjugated molecules have attracted considerable attention because of their prominent electroluminescent characteristics and simple, low-cost manufacturing. These materials can be applied widely in various optoelectronic devices, such as organic light-emitting diodes (OLEDs) [1], organic field-effect transistors [2], organic photovoltaics [3], and organic lasers [4][5][6][7][8][9][10]. Organic lasers, a significant class of organic light emitters for flat-panel displays [11], are attractive and challenging research topics.…”