The phrase 'dejected by' is correct and can be used in written English.
It is used to express the feeling of being disheartened or discouraged by something. For example: She was dejected by her poor test result.
Kilbane was dejected by his omission but understood.
Reyes appeared dejected by the news, but agreed that it was the right thing to do.
For months, Villa has appeared dejected by his inability to score.
Smith insisted that South Africa were not dejected by the result.
They never were ill, or at all dejected, By all admired, and by some respected. . . .
Others say that he has become so dejected by recent events that he wants to quit politics altogether.
Long after I had asked the paramedics to stop chest compressions, I was more dejected and frustrated by this patient's death than by almost any I had experienced as a physician.
And yet I'm much more taken by that dejected, surrendering last question than by the crowd-pleasing opening.
But as the final set wore on the cheers became less frequent and at the end there was just dejected silence, punctuated by the odd half hearted shout.
During the second intermission, the Rangers talked about staying within their system and not being dejected about trailing by one goal.
Later, Mr. Drigant's grandson walked by, looking dejected.
