OLED, , >>
߱ ڿ ߱ ذ , ߱ ȿ ϴ ġ ˴ϴ. ߱ ʿ (blocking layer) ġϴµ, ʿ (Electron Blocking Layer, EBL), ʿ (Hole Blocking Layer, HBL) Ǹ, ̵ ڿ ذ ϴ մϴ. 庮 ̱ ߱ LUMO , HOMO ƾ . ̳ LUMO HOMO Ͽ ֽϴ. Ư, Ͽ ϴ , ñ ϱ 尸 Ŀ ϸ, ̸ HOMO Ʒ, LUMO 鼭 ڿ ϱ մϴ.
OLED, , ߱ , ߱ Ͽ>>
. (thermal radiation) ߱ (luminescence). , µ ü µ ϸ ̳ , ڿ ¾ ǥԴϴ. ϴ , Ʈ ؼ µ . 츮 Ȱ ӿ 鿭 ֽϴ. ʶƮ Ǹ鼭 . , ̶߱ ƴ ¿ , ܺηκ Ǵ ȯǴ Դϴ. ڰ ٴ ¿ · Ǿٰ ٽ ȭǸ鼭 ַ ϴ . ΰǴ Ƿ پѵ , ̳ ( Ȥ ), Ȥ ڿ ڼ, ȭ Ȥ ȭ , 缱 ַ ª 뿪 ڱ, Ͽ Ǹ, ߱(Photo-Luminescence, PL), ߱(mechano-luminescence), 缱 ߱(radio-luminescence), (thermo-luminescence), ߱(Cathodo-Luminescence, CL), ߱(Electro-Luminescence, EL), ȭ ߱(chemo-luminescence) ˴ϴ.
̷ ߱ ⱸ ߿ OLED ϴµ, 帣 ڿ ν ڰ ȭ · ư鼭 . 帣 Ȯ ˴ϴ. , ذ κ ڿ ִ , Ե , ̵Ű , صκ ڿ , (exciton) , ߱ Ͽ . ⼭ ڶ ‘ (excited state)’ ̸, ¶ ‘ڰ Ͽ ʰ ’ Ǯ̵˴ϴ. ̷ ´ Ҿ ·, ڴ ¸ ãư Ư ־ ‘ (ground state)’ ٽ ư . ڰ ¿ · ư鼭 ٽ Ǵµ, پ κ · ϴ. ̶߱, ڵ , Ư ¿ ٴ · ȸϴ° , پ ߱ ⱸ ߰ߵǰų εǰ ִ , ǥ ߱ ⱸδ , (fluorescence), α(phosphorescence) ֽϴ. ǥ ߱ ⱸ ؼ ٷ ڿ ϰڽϴ.
OLED ߱, 翡 ̾߱Դ . ߱ 縦 зϿ . ڿ ڷ з , α , (single component) ȣƮ- Ʈ(host-guest type) ֽϴ. α ̾ ̸, ȣƮ-ԽƮ̶ ȣ Ʈ شϴ ԽƮ Ʈ , ߱ ̵ ߱ մ . ȣƮ Ư 켱 õǰ, ԽƮ ߱ ȿ Ǹ鼭 ߱ Ư . ȣƮ ߱ ɺٴ ڸ ̼, ȭ . ԽƮ, Ʈ ۾ а ϰ Ǵ Ư մϴ. ̿ Բ ȣƮκ ԽƮ ڸ , ߱ ̷ ϹǷ , ߱ Ư ȭǾ ȿ شȭ ֽϴ. ߱ , ڿ OLED ̾߱ ϴ ̷ ΰڽϴ.
OLED, , ߱, α>>
OLED ߱ ´ Ͻ Ҿ ·, ڴ ¸ ãư Ư ־ ‘ (ground state)’ ٽ ư . ڰ ¿ · ǵ 鼭 ٽ Ǵµ, پ κ · ˴ϴ.
¿ ڿ , Ȥ Ŀ︮ Ÿ · ϴ. , ݴ , Ī̸ ڱ ڼ 0 ¿ ڼ 1 ° ش. ϳ̾ (singlet), ̾ 3(triplet)̶ Ǿ ϴ. . HOMO LUMO ϴ ij , ڼ S մϴ. , ߵ(spin-multiplicity) , 2S+1 2(+1/2-1/2)+1=1̸ (singlet), 2(+1/2+1/2)+1=3̸ 3(triplet) Ǿ, ڿ ¿ װ 3 1 : 3 ־ ϴ. , HOMO LUMO ϴ ij еǴµ, 2 0 ǵ ݴ ̸ ش. ڴ 3 Ƿ 1 : 3 ˴ϴ.
, ڿ ӵ ſ ̸, ̴ (fluorescence) شմϴ. ݸ鿡 3 ڵ ڿ ӵ ſ α(phosphorescence) Ǵµ, ̳ Ȥ ο սǷ Ÿ. , Ϲ OLED ߱ Ͼ Ǹ, ȿ ߿ ϳ, , 25% ִ밡 ˴ϴ. , 쿡 ܺ Ǵ ȿ 20~30% ѵ , ִ ܺ ȿ 5~7.5% Ұϰ ˴ϴ.
߱ ⱸ α ڽϴ. HOMO κ ڴ öٰ LUMO ǰ, ̷ ¿ ٽ HOMO . S1, S2 κ (vibrational relaxation) ġ , S1 ٴ ġ ̸ S0 ϴ. Ͽ ݵ , RGB Ʈ Ǿ ߱ Ƿ ȿ ִ 25% 谡 ֽϴ. 75% ϴ 3 ߱ Ȱ ֵ α ʿϿ.
, δ ȿ ִġ, , 25% Ѱ谡 Ƿ, 75% ȰϷ Ǿ, ħ 1998, ̱ ϴ, Ʈ(S.R.Forest) 쿡 (platinum) ÷ Ʈ ϸ鼭 α OLED ȿ ϰ ˴ . , ݰ ߱ݼӿ - ˵ ȣ ۿ(spin-orbit coupling) , ̷ Ͽ 3 ڸ ӵ, ũ ̷ ν ߱ ֵ Ͽϴ. ̿ Ͽ ڰ 谣 (Inter-System Crossing, ISC) Ͽ 3 ڷ ȯϴ ݵǾ. ̸ Ͽ ڵ ߱ ϰ Ǿ ̷ ȿ, 100% ϰ ˴ϴ.
, α ڰ S1 3 T1 谣 (Inter- System Crossing, ISC) ϴ Ϳ Ե˴ϴ. ¿ 3 T2, T3 پ . ٸ, T0 ´ Ƿ ݵ T1 S0 ;߸ մϴ.
, α T1 S0 ̰ , ̷ ȭ ϹǷ Ģ(selection rule) ڿ迡 (forbidden transition) شմϴ. , ߱ ȿ ̷ Ǵ 3 ߱ ̿ Ǿ߸ ϰ, ̸ Ͽ ߿ ȿ (heavy atom effect) ̿, ſ ݼӿҵ ū ڱ Ʈ ν ȭ, ڼ ȣ ٲ ݰ . ַ ̰ ū (Re), (Pt), (Os), Ǿ(Eu), ̸(Ir), ͺ(Tb) α Ʈ Ǿ α ̸ Ȱ ֵ մϴ. ̷ ν 1/4 شϴ 25% , ڸ ̿ Ͽµ, α 75% ߱ ̿ ־ ȿ 100% ֽϴ. , ʷ α OLED ǰ , ƽԵ Ķ û Բ Ʈ ҿϿ Ȯ ް ֽϴ. ߱ݼ ϹǷ , ȯ . ̿ Բ α Ʈ ݰ Ư 鵵 δ ǰ ֽϴ.
Ư ߵ ִ ߱ ⱸ Ȱȭ (Thermally Activated Delayed Fluorescence, TADF)̸, ̴ 2012, Ϻ Խ ƴġ ǥ ķ ȿ ǰ . Ͽ ֱٿ ȿ ذ ɼ ִ (hyper fluorescence) ǥǾϴ. ȿ, ȭ OLED ̸, Ư ȭ(burn-in), Ȥ ȭ ȭ (image sticking) ذ Ͽ ο õǰ ֽϴ. ؼ Ʈ ̾߱⸦ ϴ.
<ȣ ̾ >
“ ְ ظ ϰ , ο ڷ پϿ ǥ , ٶϴ.”
<۱ڨ 'öƽ̾' - .>
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